This isn't an islamist thing. I really find nothing that objectionable. It is a political assassination, which is fair game. What is not fair game is targeting civilians. Since Russia is involved in the bombing of Syria, it is fair game to assassinate the diplomat. In fact, I would have more respect for Islam if they did more targeted assassinations of government officials instead of attacking random people on the street.
This is one of the best photos of an assassin I've ever seen. Now, Turkey is a NATO country and Russia is not. This could lead to something unpleasant indeed. Good thing HRC is not in charge.